I've been vegan for 12 years and have had 3 babies during that time. I didn't have any problems with any of the pregnancies, other than slightly low iron levels right at the end, not low enough to prescribe iron for. It's definitely possible to be vegan/ vegetarian throughout your pregnancy, I have many friends who had vegan or vegetarian pregnancies, too, with no problems.
I find lentils to be a quick, easy, and great source of protein and iron, and eating them with quinoa is a great way to make sure you are getting complete protein. Eating a wide variety of fruits and veggies is also really important.
A lot of vegetarians tend to sub dairy (esp cheese) for meat in a lot of dishes, don't know if you are doing this but it's definitely not the healthiest way to go, stick to legumes or nuts/ seeds instead, they have a lot more good stuff in them than the dairy. I also avoid simple carbs as much as possible and eat lots of whole and sprouted grains, and lots of quinoa. They have lots of protein and vitamins/ minerals.
I often use this site to find out which foods have what types of nutrients, it is really handy, especially for fruits and veggies: